Transfer media, network topologies

Presently possible transfer media in LANs simple twisted-pair wires, coaxial cable, and fiber optic cables, are characterized in Table I more in detail. 

Twisted-pair cable Coaxial cable Fiberoptic 

coaxial cable with baseband transmission is the most frequently used technique in implementations of LANs, in Ethernet LANs as well as in token ring networks. Transmission rates are mostly between 6 and 16 Mbits/s. Interfacing to coaxial cable is rather simple, especially with Ethernet new nodes can be connected to an existing cable without interrupting the operation of the network. 

Interfacing nodes to fiber optic networks is more complicated and expensive therefore, up to now fiber optic lines are mainly used to bridge larger distances between local segments of networks. 

Topologies. The traditional way of connecting smaller computers to a central mainframe system has been the star topology, sometimes in the form of hierarchical trees. Other networks have been built with many point-to-point connections and 

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